Abstract

We demonstrate strong coupling of single photons emitted by individual molecules at cryogenic and ambient conditions to individual nanoparticles. We provide images obtained both in transmission and reflection, where an efficiency greater than 55% was achieved in converting incident narrow-band photons to plasmon-polaritons (plasmons) of a silver nanoparticle. Our work paves the way to spectroscopy and microscopy of nano-objects with sub-shot noise beams of light and to triggered generation of single plasmons and electrons in a well-controlled manner.

This value is larger than that expected from a simple estimate of the diffraction limit because of 1) the inherently larger FWHM that is obtained in transmission measurements and 2) the lower effective numerical aperture due a smaller beam diameter in this experiment.

C. F. Bohren, and D. R. Huffman, Absorption and Scattering of Light by Small Particles (John Wiley and Sons, 1983).

This value is larger than that expected from a simple estimate of the diffraction limit because of 1) the inherently larger FWHM that is obtained in transmission measurements and 2) the lower effective numerical aperture due a smaller beam diameter in this experiment.

(a) Single dye molecules embedded in a thin organic matrix at T=1.4 K produce a beam of single photons. This beam is collected and collimated by a solid-immersion lens and an aspherical lens inside the cryostat and then coupled into a single-mode fiber (SMF). The output of this fiber is sent to the sample in a room-temperature microscope. Two avalanche photodiodes rAPD and tAPD register the signal in reflection and transmission, respectively. A spectrometer records the plasmon spectrum of a particle upon illumination by a white-light source. DM: dichroic mirror, BS: beam splitter. (b) The red curve shows the experimentally measured plasmon spectrum of the particle studied in the first experiment. The blue curve displays a theoretical spectrum corresponding to an ellipsoidal silver particle with long and short axes of 94 and 46 nm, respectively. The black curve shows the spectrum of the narrow-band single-photon source. (c) Electron microscope image of a typical silver spheroid.

Transmission (a) and reflection (b) images obtained when the sample was scanned laterally across the focus of a laser beam at a speed of 10 ms per pixel. (c) Cross sections from (a) and (b). Average of 12 transmission (d) and reflection (e) images obtained when the sample was laterally scanned in the focus of the single-photon beam at 40 ms per pixel. (f) Cross sections from (d) and (e). Light beams were polarized along the vertical directions of the images in (a), (b), (d), and (e). Scale bars correspond to 500 nm.

a) A raster-scan image of a silver nanoparticle illuminated by single photons from a terrylene molecule at room temperature. The black region at the bottom indicates loss of signal caused by the photobleaching of the molecule. b) A cross section from part (a). The inset displays the emission spectrum of a single terrylene molecule.